
window.dhtmlHistory = {
   initialize: function() {
      
      if (this.isInternetExplorer() == false) {
         return;
      }
      // if this is the first time this page has loaded...
      if (historyStorage.hasKey("DhtmlHistory_pageLoaded") == false) {
         this.fireOnNewListener = false;
         this.firstLoad = true;
         historyStorage.put("DhtmlHistory_pageLoaded", true);
      }
      // else if this is a fake onload event
      else {
         this.fireOnNewListener = true;
         this.firstLoad = false;   
      }
   },
             
   addListener: function(callback) {
      this.listener = callback;
     
      if (this.fireOnNewListener == true) {
         this.fireHistoryEvent(this.currentLocation);
         this.fireOnNewListener = false;
      }
   },
   
  add: function(newLocation, historyData) {
      var self = this;
      var addImpl = function() {
         if (self.currentWaitTime > 0)
            self.currentWaitTime = self.currentWaitTime - self.WAIT_TIME;
            
         newLocation = self.removeHash(newLocation);
         
         var idCheck = document.getElementById(newLocation);
         if (idCheck != undefined || idCheck != null) {
            var message = 
               "Exception: History locations can not have "
               + "the same value as _any_ id's "
               + "that might be in the document, "
               + "due to a bug in Internet "
               + "Explorer; please ask the "
               + "developer to choose a history "
               + "location that does not match "
               + "any HTML id's in this "
               + "document. The following ID "
               + "is already taken and can not "
               + "be a location: " 
               + newLocation;
               
            throw message; 
         }
         
         // store the history data into history storage
         historyStorage.put(newLocation, historyData);
         
         // indicate to the browser to ignore this upcomming 
         // location change
         self.ignoreLocationChange = true;
 
         // indicate to IE that this is an atomic location change
         // block
         this.ieAtomicLocationChange = true;
                 
         // save this as our current location
         self.currentLocation = newLocation;
         
         // change the browser location
         window.location.hash = newLocation;
         
         // change the hidden iframe's location if on IE
         if (self.isInternetExplorer())
            self.iframe.src = "blank.html?" + newLocation;
            
         // end of atomic location change block
         // for IE
         this.ieAtomicLocationChange = false;
      };

      // now execute this add request after waiting a certain amount of time, so as to
      // queue up requests
      window.setTimeout(addImpl, this.currentWaitTime);
   
      // indicate that the next request will have to wait for awhile
      this.currentWaitTime = this.currentWaitTime + this.WAIT_TIME;
   },
   
   /** public */ isFirstLoad: function() {
      if (this.firstLoad == true) {
         return true;
      }
      else {
         return false;
      }
   },
   
   /** public */ isInternational: function() {
      return false;
   },
   
   /** public */ getVersion: function() {
      return "0.05";
   },
   
   /** public */ getCurrentLocation: function() {
      var currentLocation = this.removeHash(window.location.hash);
         
      return currentLocation;
   },
   
   /** private */ currentLocation: null,
   
   /** Our history change listener. */
   /** private */ listener: null,
   
   /** private */ iframe: null,
   
   /** private */ ignoreLocationChange: null,
 
   
   /** private */ WAIT_TIME: 200,

   /** private */ currentWaitTime: 0,
   

   /** private */ fireOnNewListener: null,
   

   /** private */ firstLoad: null,
   
   /** private */ ieAtomicLocationChange: null,          
   
   /** private */ create: function() {
      // get our initial location
      var initialHash = this.getCurrentLocation();
      
      this.currentLocation = initialHash;
      
      if (this.isInternetExplorer()) {
         document.write("<iframe style='border: 0px; width: 1px; "
                               + "height: 1px; position: absolute; bottom: 0px; "
                               + "right: 0px; visibility: visible;' "
                               + "name='DhtmlHistoryFrame' id='DhtmlHistoryFrame' "
                               + "src='blank.html?" + initialHash + "'>"
                               + "</iframe>");
         this.WAIT_TIME = 400;
      }
      
    
      var self = this;
      window.onunload = function() {
         self.firstLoad = null;
      };
      
      if (this.isInternetExplorer() == false) {
         if (historyStorage.hasKey("DhtmlHistory_pageLoaded") == false) {
            this.ignoreLocationChange = true;
            this.firstLoad = true;
            historyStorage.put("DhtmlHistory_pageLoaded", true);
         }
         else {
            // indicate that we want to pay attention
            // to this location change
            this.ignoreLocationChange = false;
            // For browser's other than IE, fire
            // a history change event; on IE,
            // the event will be thrown automatically
            // when it's hidden iframe reloads
            // on page load.
            // Unfortunately, we don't have any 
            // listeners yet; indicate that we want
            // to fire an event when a listener
            // is added.
            this.fireOnNewListener = true;
         }
      }
      else { // Internet Explorer
         // the iframe will get loaded on page
         // load, and we want to ignore this fact
         this.ignoreLocationChange = true;
      }
      
      if (this.isInternetExplorer()) {
            this.iframe = document.getElementById("DhtmlHistoryFrame");
      }                                                              

      // other browsers can use a location handler that checks
      // at regular intervals as their primary mechanism;
      // we use it for Internet Explorer as well to handle
      // an important edge case; see checkLocation() for
      // details
      var self = this;
      var locationHandler = function() {
         self.checkLocation();
      };
      setInterval(locationHandler, 100);
   },
   
   /** Notify the listener of new history changes. */
   /** private */ fireHistoryEvent: function(newHash) {
      // extract the value from our history storage for
      // this hash
      var historyData = historyStorage.get(newHash);

      // call our listener      
      this.listener.call(null, newHash, historyData);
   },
   
   /** Sees if the browsers has changed location.  This is the primary history mechanism
       for Firefox. For Internet Explorer, we use this to handle an important edge case:
       if a user manually types in a new hash value into their Internet Explorer location
       bar and press enter, we want to intercept this and notify any history listener. */
   /** private */ checkLocation: function() {
      // ignore any location changes that we made ourselves
      // for browsers other than Internet Explorer
      if (this.isInternetExplorer() == false
         && this.ignoreLocationChange == true) {
         this.ignoreLocationChange = false;
         return;
      }
      
      // if we are dealing with Internet Explorer
      // and we are in the middle of making a location
      // change from an iframe, ignore it
      if (this.isInternetExplorer() == false
          && this.ieAtomicLocationChange == true) {
         return;
      }
      
      // get hash location
      var hash = this.getCurrentLocation();
      
      // see if there has been a change
      if (hash == this.currentLocation)
         return;
         
      // on Internet Explorer, we need to intercept users manually
      // entering locations into the browser; we do this by comparing
      // the browsers location against the iframes location; if they
      // differ, we are dealing with a manual event and need to
      // place it inside our history, otherwise we can return
      this.ieAtomicLocationChange = true;
      
      if (this.isInternetExplorer()
          && this.getIFrameHash() != hash) {
         this.iframe.src = "blank.html?" + hash;
      }
      else if (this.isInternetExplorer()) {
         // the iframe is unchanged
         return;
      }
         
      // save this new location
      this.currentLocation = hash;
      
      this.ieAtomicLocationChange = false;
      
      // notify listeners of the change
      this.fireHistoryEvent(hash);
   },  

   /** Gets the current location of the hidden IFrames
       that is stored as history. For Internet Explorer. */
   /** private */ getIFrameHash: function() {
      // get the new location
      var historyFrame = document.getElementById("DhtmlHistoryFrame");
      var doc = historyFrame.contentWindow.document;
      var hash = new String(doc.location.search);

      if (hash.length == 1 && hash.charAt(0) == "?")
         hash = "";
      else if (hash.length >= 2 && hash.charAt(0) == "?")
         hash = hash.substring(1); 
    
    
      return hash;
   },          
   
   /** Removes any leading hash that might be on a location. */
   /** private */ removeHash: function(hashValue) {
      if (hashValue == null || hashValue == undefined)
         return null;
      else if (hashValue == "")
         return "";
      else if (hashValue.length == 1 && hashValue.charAt(0) == "#")
         return "";
      else if (hashValue.length > 1 && hashValue.charAt(0) == "#")
         return hashValue.substring(1);
      else
         return hashValue;     
   },          
   
   /** For IE, says when the hidden iframe has finished loading. */
   /** private */ iframeLoaded: function(newLocation) {
      // ignore any location changes that we made ourselves
      if (this.ignoreLocationChange == true) {
         this.ignoreLocationChange = false;
         return;
      }
      
      // get the new location
      var hash = new String(newLocation.search);
      if (hash.length == 1 && hash.charAt(0) == "?")
         hash = "";
      else if (hash.length >= 2 && hash.charAt(0) == "?")
         hash = hash.substring(1);
      
      // move to this location in the browser location bar
      // if we are not dealing with a page load event
      if (this.pageLoadEvent != true) {
         window.location.hash = hash;
      }

      // notify listeners of the change
      this.fireHistoryEvent(hash);
   },
   
   /** Determines if this is Internet Explorer. */
   /** private */ isInternetExplorer: function() {
      var userAgent = navigator.userAgent.toLowerCase();
      if (document.all && userAgent.indexOf('msie')!=-1) {
         return true;
      }
      else {
         return false;
      }
   }
};












/** An object that uses a hidden form to store history state 
    across page loads. The chief mechanism for doing so is using
    the fact that browser's save the text in form data for the
    life of the browser and cache, which means the text is still
    there when the user navigates back to the page. See
    http://codinginparadise.org/weblog/2005/08/ajax-tutorial-saving-session-across.html
    for full details. */
window.historyStorage = {
   /** If true, we are debugging and show the storage textfield. */
   /** public */ debugging: false,
   
   /** Our hash of key name/values. */
   /** private */ storageHash: new Object(),
   
   /** If true, we have loaded our hash table out of the storage form. */
   /** private */ hashLoaded: false, 
   
   /** public */ put: function(key, value) {
       this.assertValidKey(key);
       
       // if we already have a value for this,
       // remove the value before adding the
       // new one
       if (this.hasKey(key)) {
         this.remove(key);
       }
       
       // store this new key
       this.storageHash[key] = value;
       
       // save and serialize the hashtable into the form
       this.saveHashTable(); 
   },
   
   /** public */ get: function(key) {
      this.assertValidKey(key);
      
      // make sure the hash table has been loaded
      // from the form
      this.loadHashTable();
      
      var value = this.storageHash[key];

      if (value == undefined)
         return null;
      else
         return value; 
   },
   
   /** public */ remove: function(key) {
      this.assertValidKey(key);
      
      // make sure the hash table has been loaded
      // from the form
      this.loadHashTable();
      
      // delete the value
      delete this.storageHash[key];
      
      // serialize and save the hash table into the 
      // form
      this.saveHashTable();
   },
   
   /** Clears out all saved data. */
   /** public */ reset: function() {
      this.storageField.value = "";
      this.storageHash = new Object();
   },
   
   /** public */ hasKey: function(key) {
      this.assertValidKey(key);
      
      // make sure the hash table has been loaded
      // from the form
      this.loadHashTable();
      
      if (typeof this.storageHash[key] == "undefined")
         return false;
      else
         return true;
   },
   
   /** Determines whether the key given is valid;
       keys can only have letters, numbers, the dash,
       underscore, spaces, or one of the 
       following characters:
       !@#$%^&*()+=:;,./?|\~{}[] */
   /** public */ isValidKey: function(key) {
      // allow all strings, since we don't use XML serialization
      // format anymore
      return (typeof key == "string");
      
      /*
      if (typeof key != "string")
         key = key.toString();
      
      
      var matcher = 
         /^[a-zA-Z0-9_ \!\@\#\$\%\^\&\*\(\)\+\=\:\;\,\.\/\?\|\\\~\{\}\[\]]*$/;
                     
      return matcher.test(key);*/
   },
   
   
   
   
   /** A reference to our textarea field. */
   /** private */ storageField: null,
   
   /** private */ init: function() {
      // write a hidden form into the page
      var styleValue = "position: absolute; top: -1000px; left: -1000px;";
      if (this.debugging == true) {
         styleValue = "width: 30em; height: 30em;";
      }   
      
      var newContent =
         "<form id='historyStorageForm' " 
               + "method='GET' "
               + "style='" + styleValue + "'>"
            + "<textarea id='historyStorageField' "
                      + "style='" + styleValue + "'"
                              + "left: -1000px;' "
                      + "name='historyStorageField'></textarea>"
         + "</form>";
      document.write(newContent);
      
      this.storageField = document.getElementById("historyStorageField");
   },
   
   /** Asserts that a key is valid, throwing
       an exception if it is not. */
   /** private */ assertValidKey: function(key) {
      if (this.isValidKey(key) == false) {
         throw "Please provide a valid key for "
               + "window.historyStorage, key= "
               + key;
       }
   },
   
   /** Loads the hash table up from the form. */
   /** private */ loadHashTable: function() {
      if (this.hashLoaded == false) {
         // get the hash table as a serialized
         // string
         var serializedHashTable = this.storageField.value;
         
         if (serializedHashTable != "" &&
             serializedHashTable != null) {
            // destringify the content back into a 
            // real JavaScript object
            this.storageHash = eval('(' + serializedHashTable + ')');  
         }
         
         this.hashLoaded = true;
      }
   },
   
   /** Saves the hash table into the form. */
   /** private */ saveHashTable: function() {
      this.loadHashTable();
      
      // serialized the hash table
      var serializedHashTable = JSON.stringify(this.storageHash);
      
      // save this value
      this.storageField.value = serializedHashTable;
   }   
};










/** The JSON class is copyright 2005 JSON.org. */
Array.prototype.______array = '______array';

var JSON = {
    org: 'http://www.JSON.org',
    copyright: '(c)2005 JSON.org',
    license: 'http://www.crockford.com/JSON/license.html',

    stringify: function (arg) {
        var c, i, l, s = '', v;

        switch (typeof arg) {
        case 'object':
            if (arg) {
                if (arg.______array == '______array') {
                    for (i = 0; i < arg.length; ++i) {
                        v = this.stringify(arg[i]);
                        if (s) {
                            s += ',';
                        }
                        s += v;
                    }
                    return '[' + s + ']';
                } else if (typeof arg.toString != 'undefined') {
                    for (i in arg) {
                        v = arg[i];
                        if (typeof v != 'undefined' && typeof v != 'function') {
                            v = this.stringify(v);
                            if (s) {
                                s += ',';
                            }
                            s += this.stringify(i) + ':' + v;
                        }
                    }
                    return '{' + s + '}';
                }
            }
            return 'null';
        case 'number':
            return isFinite(arg) ? String(arg) : 'null';
        case 'string':
            l = arg.length;
            s = '"';
            for (i = 0; i < l; i += 1) {
                c = arg.charAt(i);
                if (c >= ' ') {
                    if (c == '\\' || c == '"') {
                        s += '\\';
                    }
                    s += c;
                } else {
                    switch (c) {
                        case '\b':
                            s += '\\b';
                            break;
                        case '\f':
                            s += '\\f';
                            break;
                        case '\n':
                            s += '\\n';
                            break;
                        case '\r':
                            s += '\\r';
                            break;
                        case '\t':
                            s += '\\t';
                            break;
                        default:
                            c = c.charCodeAt();
                            s += '\\u00' + Math.floor(c / 16).toString(16) +
                                (c % 16).toString(16);
                    }
                }
            }
            return s + '"';
        case 'boolean':
            return String(arg);
        default:
            return 'null';
        }
    },
    parse: function (text) {
        var at = 0;
        var ch = ' ';

        function error(m) {
            throw {
                name: 'JSONError',
                message: m,
                at: at - 1,
                text: text
            };
        }

        function next() {
            ch = text.charAt(at);
            at += 1;
            return ch;
        }

        function white() {
            while (ch != '' && ch <= ' ') {
                next();
            }
        }

        function str() {
            var i, s = '', t, u;

            if (ch == '"') {
outer:          while (next()) {
                    if (ch == '"') {
                        next();
                        return s;
                    } else if (ch == '\\') {
                        switch (next()) {
                        case 'b':
                            s += '\b';
                            break;
                        case 'f':
                            s += '\f';
                            break;
                        case 'n':
                            s += '\n';
                            break;
                        case 'r':
                            s += '\r';
                            break;
                        case 't':
                            s += '\t';
                            break;
                        case 'u':
                            u = 0;
                            for (i = 0; i < 4; i += 1) {
                                t = parseInt(next(), 16);
                                if (!isFinite(t)) {
                                    break outer;
                                }
                                u = u * 16 + t;
                            }
                            s += String.fromCharCode(u);
                            break;
                        default:
                            s += ch;
                        }
                    } else {
                        s += ch;
                    }
                }
            }
            error("Bad string");
        }

        function arr() {
            var a = [];

            if (ch == '[') {
                next();
                white();
                if (ch == ']') {
                    next();
                    return a;
                }
                while (ch) {
                    a.push(val());
                    white();
                    if (ch == ']') {
                        next();
                        return a;
                    } else if (ch != ',') {
                        break;
                    }
                    next();
                    white();
                }
            }
            error("Bad array");
        }

        function obj() {
            var k, o = {};

            if (ch == '{') {
                next();
                white();
                if (ch == '}') {
                    next();
                    return o;
                }
                while (ch) {
                    k = str();
                    white();
                    if (ch != ':') {
                        break;
                    }
                    next();
                    o[k] = val();
                    white();
                    if (ch == '}') {
                        next();
                        return o;
                    } else if (ch != ',') {
                        break;
                    }
                    next();
                    white();
                }
            }
            error("Bad object");
        }

        function num() {
            var n = '', v;
            if (ch == '-') {
                n = '-';
                next();
            }
            while (ch >= '0' && ch <= '9') {
                n += ch;
                next();
            }
            if (ch == '.') {
                n += '.';
                while (next() && ch >= '0' && ch <= '9') {
                    n += ch;
                }
            }
            if (ch == 'e' || ch == 'E') {
                n += 'e';
                next();
                if (ch == '-' || ch == '+') {
                    n += ch;
                    next();
                }
                while (ch >= '0' && ch <= '9') {
                    n += ch;
                    next();
                }
            }
            v = +n;
            if (!isFinite(v)) {
                error("Bad number");
            } else {
                return v;
            }
        }

        function word() {
            switch (ch) {
                case 't':
                    if (next() == 'r' && next() == 'u' && next() == 'e') {
                        next();
                        return true;
                    }
                    break;
                case 'f':
                    if (next() == 'a' && next() == 'l' && next() == 's' &&
                            next() == 'e') {
                        next();
                        return false;
                    }
                    break;
                case 'n':
                    if (next() == 'u' && next() == 'l' && next() == 'l') {
                        next();
                        return null;
                    }
                    break;
            }
            error("Syntax error");
        }

        function val() {
            white();
            switch (ch) {
                case '{':
                    return obj();
                case '[':
                    return arr();
                case '"':
                    return str();
                case '-':
                    return num();
                default:
                    return ch >= '0' && ch <= '9' ? num() : word();
            }
        }

        return val();
    }
};



/** Initialize all of our objects now. */
window.historyStorage.init();
window.dhtmlHistory.create();
